Recent environmental events such as the damage to New Orleans and other coastal region communities from hurricanes such as Katrina and recent major tornado, storm, forest and brush fire, flood and earthquake damage in communities in virtually every region of the country and in virtually every country have emphasized a long standing need for structures, such as houses, schools, stores, governmental, public service and medical facilities and similar structures, having significantly improved resistance to extreme environmental conditions. It is also recognized that the advent of global warming will result not only in shifting meteorological patterns and conditions, but more extreme weather conditions. For example, there is substantial support for the expectation that ordinary storms will become stronger and more frequent with higher winds and heavier rainfall, that category 4 and 5 hurricanes will become relatively common rather than rare, with the possibility of at least occasional hurricanes of even higher effective categories, and tornados and forest and brush fires will become larger, stronger and more common over larger areas, as will tornadoes and floods.
Rapidly accumulating evidence clearly shows that traditional methods for constructing houses, schools, stores, governmental, public service and medical facilities and similar structures are not adequate to meet the increased demands presented by more extreme weather conditions and that while such structures of have been and are presently built in a number of ways, the traditional methods have proven unsatisfactory for various reasons. For example, structures such as houses have commonly been built from wood, such as 2×4s and plywood nailed together or masonry elements, such as bricks, concrete blocks or concrete slabs, held together by mortar and connected to wood elements by nail-like fasteners or adhesives. While nailed wooden structures are relatively light, strong and inexpensive and while the individual components comprising the structures, such as 2×4s and sheets of plywood, are individually relatively strong, their strength is limited by the inherent properties of the materials. Wooden frame structures are also weakened, and tend to be excessively flexible, by the relatively large number of joints necessary to assemble the individual components. Also, nails are commonly used to assembly the individual components of wooden structures because nails are cheaper and easier to use than other forms of fasteners. Nails, however, do not provide joints that are as secure and rigid as those provided by more expensive forms of fasteners and nailed joints tend to flex or come apart relatively readily under various common forms of structural stress. Such measures as are typically taken to make the joints in such structures stronger and more rigid, however, such as bolts, screws, clenched nails and adhesives and combinations thereof, rapidly increase the cost and construction time of the structures. It should also be noted that some of the alternate forms of fasteners, such as the web plates that are often used to assemble rafters and joists and that have large numbers of short protruding spike elements that are driven into abutting joists, typically provide a joint that has strength along only one axis or plane.
Masonry structures, which are typically constructed from a combination of wooden structural elements, such as roofs and floors, and masonry elements such as bricks, blocks and slabs bound together and to the wooden elements by mortar or specialized fasteners, suffer from similar problems, as well as being heavier and more expensive to construct. While such structures may be initially stronger and more rigid than wooden structures, such structures often include even more joints than wooden structures, such as the joints between bricks and blocks, and mortar, for example, is very subject to cracking and sudden failure once a stress limit is reached. In addition, masonry structures are susceptible to stresses that more flexible wooden structures will survive, such as stresses caused by earth movements, such as caused by earthquakes or by wave or landslide erosion, and masonry buildings, unlike wooden structures, will often fail catastrophically and almost completely once failure has started. It must be further noted that masonry structures of often subject to cracking with temperature induced expansion and contraction, as well as settling, and often present ventilation problems, resulting in excess humidity, condensation and possible mold growth.
Structures such as houses, schools, stores, governmental, public service and medical facilities and similar structures have also been constructed from modular iron or steel elements fastened together, for example, with metal pins or bolts or by welding. While this type of structure is generally stronger and more rigid in both the elements and joints than wooden or masonry structures, the significantly greater cost and weight of the structures and the fact that such structures are significantly more difficult, complex and time consuming to construct typically renders such structures impractical except in specific, special circumstances. Other implementations of such structures may use somewhat different materials, such as aluminum or plastic, but have all been found to suffer from one or more of the above discussed disadvantages.
The above discussed problems are compounded in the case of already existing structures, many of which lack adequate resistance to hurricanes, tornadoes, storms, forest and brush fires, floods and earthquakes. In some instances it is possible to replace existing structures with new construction meeting the necessary environmental resistance criteria. In many cases, however, it is not possible or feasible to replace existing structures because of, for example, economic, legal, zoning or site restrictions and it is necessary to modify or adapt the existing structures to provide improved resistance to environmental factors. The adaptation or modification of an existing structure to provide improved structural resistance against wind, fire, flood or earthquake damage is a very different matter from the construction of a new structure as it is necessary to work around an existing structure, which will often restrict or interfere with the necessary structural modifications.
The modular structural system of the present invention as described herein below provides solutions to these and other problems of the prior art.